package casino;
import java.util.*;

public class CheatedSlotMachine_1 {
	public static void main(String[] args){
		Set<Integer> testSet = new HashSet<Integer>(); 
		for(int i = 0; i < 10; ++i){
			testSet.add(new Integer(i));
		}
		Iterator i = testSet.iterator();

		int output = 0;	
		for(int j = 0; j < 10 && i.hasNext(); ++j){
			output += (Integer)i.next();
			testSet.add(new Integer(j));
		}
		System.out.println(output);
	}
}
